Lower urinary tract (LUT) dysfunction can include an overactive bladder (OAB). The bladder's smooth muscle is referred to as the detrusor muscle. The main symptoms of an overactive bladder are an increased day-time and night-time frequency of urination, an increased frequency of the urge to urinate and a reduced ability to control urination. OAB is increasing in the ageing population and there are few highly-effective or tolerable treatments (Kelleher C J, Kreder K J, Pleil A M, Burgess S M, Reese P R, “Health-related quality of life of patients receiving extended-release tolterodine for overactive bladder” Am J Manag. Care 2002; 8: S608-15).
A cause of OAB may be a frequent or an excessive release of acetylcholine from cholinergic nerves innervating or terminating near the bladder smooth muscle. A common pharmaceutical therapy for OAB is administration of an anti-muscarinic drug to block the excessive acetylcholine from binding to acetylcholine receptors. Unfortunately, such anti-muscarinic therapy has only a 65-75% efficacy in treating major symptoms of overactive bladder (OAB) in a patient, and its use is limited due to drug side effects such as blurred vision, dry mouth and constipation. (Zhang, X, Kuppam, DSR, Melman, A, DiSanto, M E. “In vitro and In vivo relaxation of urinary bladder smooth muscle by the selective Myosin II inhibitor, blebbistatin” BJU Internat. e-publication 2010, journal publication, 2011; Volume 107, Issue 2, pages 310-317). About 75% of the OAB patients discontinue taking an anti-muscarinic drug to treat OAB because the patient finds such side effects intolerable.
Various types of drugs for a treatment of OAB include using α-adrenergic antagonists, β-adrenoceptor agonists, membrane channel activity modulators, phosphodiesterase inhibitors, and prostaglandin-synthesis inhibitors (Andersson K E, Chapple C R, Cardozo L et al. “Pharmacological treatment of overactive bladder: report from the International Consultation on Incontinence” Curr Opin Urol 2009; 19: 380-94). Some pharmaceutical drug therapies for OAB modify the myogenic pathway of the bladder's smooth muscle (detrusor muscle) (Yoshimura N, Kaiho Y, Miyazato M et al. “Therapeutic receptor targets for lower urinary tract dysfunction.” Naunyn Schmiedebergs Arch Pharmacol 2008; 377: 437-48). Myogenic pathways are believed to be an important trigger for detrusor muscle contraction and relaxation cycling. In smooth muscle there are changes in cell membrane tension during the muscle contraction and relaxation cycle. The stretch declines during muscle contraction and increases during muscle relaxation. Increased membrane tension opens membrane ion channels whose conductance depolarizes the cell transmembrane potential. The change in transmembrane potential increases cytoplasmic calcium ion levels and other biochemical processes which stimulate muscle contraction. Contraction relieves membrane tension and the processes reverse during muscle relaxation when membrane tension has again increased due to muscle lengthening. Different smooth muscle organs vary in degree, frequency and time profile of their contractions. The response of different smooth muscles to drugs is unpredictable. It is appreciated that there is serial and parallel biochemical signal processing and often with positive and negative feedback controls. Also, there can be changes in genetic expression of smooth muscle during development and aging. Endocrine and exocrine processes also modulate smooth muscle function. It is not obvious how to develop an effective and tolerable pharmaceutical treatment for an over-active bladder smooth muscle.